When a film is formed on a wafer with plasma, there is a problem of a distance between a plasma generator generating the plasma and the wafer. If the distance is too short, it causes the wafer to suffer damage due to the plasma, which may result in poor quality of the formed film. On the other hand, if the distance is too long, it causes a formation rate of the formed film to be slow, which causes the formation of the film to take a long time. Moreover, when the film is formed on the wafer with the plasma, X-rays arising from the plasma may cause defects in the wafer.